//水平居中
@mixin horizontally {
    margin-left: auto;
    margin-top : auto;
}
//绝对居中
@mixin absoluteCenter{
    position: absolute;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;
    margin: auto;
}

@mixin clearboth {
    content: "";
    display: block;
    clear: both;
    overflow: hidden;
}

@mixin transform( $arg : left 0s ){
    -webkit-transform: $arg;
    -o-transform: $arg;
    -ms-transform: $arg;
    -moz-transform: $arg;
    transform: $arg;
}